OpenBSD/vax on SIMH

It is very easy to install OpenBSD/vax on the
SIMH VAX simulator. All
you need is a reasonably fast machine, enough disk space for a 1.5GB
disk image and the vax floppy53.fs file.
Assuming you're going to run SIMH on an OpenBSD system, install the
emulators/simh package from ports.
Decide on an appropriate location for your OpenBSD/vax SIMH
environment and at that location, create a file openbsd.simh
with the following contents:

This configures SIMH to simulate a VAX with a whopping 128 MB of
memory, a RA92 1.5GB disk, a CD-ROM unit to hold CD1 of your CD-ROM
set, another CD-ROM unit to boot from, and a DELQA Qbus Ethernet
controller attached to the tun0 interface.
You might need to replace /dev/rcd0c with the
name of the raw device corresponding to your real CD-ROM unit.

By default pressing ^E will interrupt the emulation; if you're
accustomed to the emacs editing keys, you might like to remap this
(e.g. adding set console wru=1e sets it to ^6,
ascii code 0x1e).
If you prefer a larger disk, replace set rq0 ra92
with e.g. set rq0 rauser=15000 (where 15000 is the
size in MB).
See the SIMH documentation for more details.

Before starting SIMH, you will need to configure the network.
In most cases, the following bridge-based configuration will give
best results:

Create the tun0 network interface, set it into layer 2 mode and bring it up:

By setting appropriate permissions on /dev/tun0 you can avoid running
SIMH as root.

Alternatively, if you cannot use bridge(4) (for example with some
wireless drivers), you can use BPF to connect to the network.
In this case, you can skip the above ifconfig lines and
replace the "at xq0 tap:tun0" line with a line like this,
replacing iwn0 with your actual network interface as necessary:

at xq0 iwn0

Copy vax/floppy53.fs to the location of your
OpenBSD/vax SIMH environment.
Now fire up SIMH. At the boot prompt you should type boot
dua2:, after which SIMH should boot into the normal OpenBSD
installation program:

to boot from your newly installed disk image. You'll need a little
patience upon your first boot, since generating the SSH host keys can
take quite a bit of time. But it will eventually boot through and
present you with a friendly login prompt:

OpenBSD/vax (noname.my.domain) (console)
login:

When you are done installing any additional packages, you might want
to remove the lines referring to your real CD-ROM unit and
floppy53.fs from your openbsd.simh file.